/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution{
    public boolean isSubtree(TreeNode root, TreeNode subRoot) {
        if(root == null || subRoot==null){
            return false;
        }
        //1、判断两棵树 是不是两颗相同的树
        if(isSameTree(root,subRoot)){
            return true;
        }
        //2、subRoot是不是 root.left 子树
        if(isSubtree(root.left,subRoot)){
            return true;
        }
        //3、subRoot是不是 root.right 子树
        if(isSubtree(root.right,subRoot)){
            return true;
        }
        return false;
    }

    public boolean isSameTree(TreeNode p, TreeNode q) {
        if(p == null && q != null  || p != null && q == null ) {
            return false;
        }
        if(p == null && q == null) {
            return true;
        }
        if(p.val != q.val) {
            return false;
        }
        return isSameTree(p.left,q.left) && isSameTree(p.right,q.right);
    }
}
 